Stanislaus County declares emergency to battle pest that could decimate tomato crops

Stanislaus County supervisors declared a local emergency Tuesday over a pest that threatens to decimate tomato crops.

A small insect called the beet leafhopper feeds on tomato plants and spreads a virus that turns the leaves yellow and stunts the growth of the plants.

Growers and pest control advisers informed the county they detected beet leafhoppers in tomato crops planted this spring, prompting Sheriff Jeff Dirkse, as county emergency services director, to proclaim an emergency Thursday.

The Board of Supervisors ratified the proclamation and recognized that the virus, called beet curly top, is an immediate threat to tomato crops, primarily in the western portion of the county.

“It is here now,” county Ag Commissioner Linda Pinfold said in recommending a response to the emergency.

The county has almost 10,000 acres of tomatoes in production, yielding a harvest valued at $53.5 million in 2022. Stanislaus and Merced, Madera, Fresno, Kings and Kern counties have declared emergencies to control beet curly top virus.

Beet leafhoppers can infect about 300 plant species, including vegetable crops and weeds. Pinfold said the tiny bugs are 3.5 millimeters long and spend the winter in grasses of the foothills. When the hills dry out, the leafhoppers migrate to the Valley floor and may become a problem in the rows of transplanted tomato plants around Patterson and Westley.

The tomato plants are particularly vulnerable when they start flowering, Pinfold said.

The emergency declaration is mostly about authorizing use of the limited pesticides available to control the pest. Regulations in California went into effect Jan. 1 to keep neonicotinoid pesticides from destroying honeybees, which are important pollinators, so the use of the pesticides is prohibited during the bloom.

However, an exception allowing neonicotinoid applications is granted in counties that declare an emergency. Growers are required to notify beekeepers within a mile if they are using the pesticides.

The county Agricultural Commissioner may authorize emergency use of neonicotinoids on tomato crops, as long as it’s coordinated with the director of emergency services.

Bianca Lopez, an environmental advocate with Valley Improvement Projects, expressed concern about the health risks of the pesticides to pregnant women and pollution of water sources. She said the county isn’t looking at alternative control methods that don’t harm the environment.

“I hope that farmers are only applying this if it’s needed,” Lopez said. “Pesticides create a vicious cycle.”

Daniel Bays, a tomato grower near Westley, said the curly top virus is not a concern every year. The rainy winter conditions followed by the foothill grasses drying out quickly most likely brought on the threat this year, he said.

“We look at all all of our (pest control) options to see what’s effective and beneficial for us,” Bays said, adding that tomatoes are an important crop for the county’s west side and for canneries.

The threat of beet leafhoppers goes back for decades in the San Joaquin Valley, with major impacts to beet crops reported in the 1920s. The California Department of Food and Agriculture created a program for control of the curly top virus in 1943.